Add the ability to follow the agent as it makes edits (#29839)

Nathan here: I also tacked on a bunch of UI refinement.

Release Notes:

- Introduced the ability to follow the agent around as it reads and
edits files.

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/debugger_ui/src/session.rs

@@ -7,11 +7,11 @@ use gpui::{App, Entity, EventEmitter, FocusHandle, Focusable, Subscription, Task
 use project::Project;
 use project::debugger::session::Session;
 use project::worktree_store::WorktreeStore;
-use rpc::proto::{self, PeerId};
+use rpc::proto;
 use running::RunningState;
 use ui::{Indicator, prelude::*};
 use workspace::{
-    FollowableItem, ViewId, Workspace,
+    CollaboratorId, FollowableItem, ViewId, Workspace,
     item::{self, Item},
 };
 
@@ -189,9 +189,9 @@ impl FollowableItem for DebugSession {
         Task::ready(Ok(()))
     }
 
-    fn set_leader_peer_id(
+    fn set_leader_id(
         &mut self,
-        _leader_peer_id: Option<PeerId>,
+        _leader_id: Option<CollaboratorId>,
         _window: &mut Window,
         _cx: &mut Context<Self>,
     ) {